The present invention relates to a battery pack arranged to make a judgment concerning a loss of functional status and to perform selectively charge-and-discharge disabling control and forced discharge control according to the judgment.
If a battery pack is continuously used after the lifetime thereof has completed its span, the capacity value reduces extremely. In addition, the battery that has been repeatedly overcharged and overdischarged involves the problem that lithium in the battery is likely to precipitate in the form of dendrite and break through the separator, making a short circuit in the battery and thus causing smoking or ignition. The same problem may arise if the battery pack is brought into an unexpected state by the user""s mistake in usage, for example, if the battery pack is disassembled or damaged with a sharp-edged metal.
Moreover, although batteries should be disposed of as industrial waste by specific disposers, there is a possibility that batteries may be disposed of as they are, together with combustible substances. In such a case, if an existing battery pack that is overcharged, for example, is brought into a dangerous state, smoking or ignition is likely to occur.
In view of the above-described problems, an object of the present invention is to judge whether or not a battery pack has lost its function owing to the completion of the span of life and a marked degradation in function and to limit the use of the battery pack judged to be unusable by executing appropriate processing.
To attain the above-described object, the present invention provides a battery pack arranged to make a judgment concerning a loss of functional status and to perform selectively charge-and-discharge control and forced discharge control according to the judgment. The battery pack includes a charge-and-discharge control device for charging and discharging a battery and a forced discharge control device for forcedly discharging each cell. A function detecting device detects a functional status of the battery pack. A judging device makes a judgment concerning a loss of functional status detected by the function detecting device. A control device selectively controls the charge-and-discharge control device and the forced discharge control device according to the judgment concerning a loss of functional status made by the judging device, whereby charge-and-discharge control and forced discharge control are selectively performed according to the judgment concerning a loss of functional status.
The function detecting device may include a timer for measuring the elapsed time since the date of manufacture. In this case, the judging device judges whether or not there is a loss of functional status according to whether or not the elapsed time is more than a predetermined value. The function detecting device may include, in addition to the timer, one of a counting device for counting the number of charge/discharge cycles, a temperature detecting device for detecting an average temperature of the battery pack, and a measuring device for measuring the charging rate of the battery pack. In this case, the elapsed time is corrected by one of the number of charge/discharge cycles, the average temperature and the charging rate. The function detecting device may include a temperature detecting device for detecting an average temperature and a timer for measuring the elapsed time since the date of manufacture in accordance with a doubling rule by which a period of time elapsed is doubled for every 10xc2x0 C. rise in the average temperature. In this case, the judging device judges whether or not there is a loss of functional status according to whether or not the elapsed time is more than a predetermined value. The function detecting device may include a counting device for counting the number of charge/discharge cycles. In this case, the judging device judges whether or not there is a loss of functional status according to whether or not the number of charge/discharge cycles is more than a predetermined value. The function detecting device may include a capacity detecting device for detecting a full-charge capacity. In this case, the judging device judges whether or not there is a loss of functional status according to whether or not the full-charge capacity is less than a predetermined value. The function detecting device may include a device for accumulating a discharge or charge capacity. In this case, the judging device judges whether or not there is a loss of functional status according to whether or not the accumulated capacity value is more than a predetermined value.
The function detecting device may include a device for measuring a temperature and an electric current. In this case, the judging device judges whether or not there is a loss of functional status according to whether or not the charge-and-discharge efficiency at a predetermined temperature and a predetermined current value measured by the device is less than a predetermined value. The function detecting device may include a device for measuring a temperature and an electric current. In this case, the judging device judges whether or not there is a loss of functional status according to whether or not the self-discharge current from the battery at a predetermined temperature measured by the device is more than a predetermined value. The function detecting device may include a device for detecting an electric current. In this case, the judging device judges whether or not there is a loss of functional status from the value of charge/discharge current measured by the device. The function detecting device may include a device for detecting a cell voltage. In this case, the judging device judges whether or not there is a loss of functional status from the value of the cell voltage. The function detecting device may include a device for detecting a battery voltage and an electric current. In this case, the judging device judges whether or not there is a loss of functional status from the battery voltage and electric current value detected by the detecting device. The function detecting device may include a device for detecting a temperature. In this case, the judging device judges whether or not there is a loss of functional status according to whether or not the temperature of the battery pack or the temperature of the cell is more than a predetermined value, or whether or not the time interval during which the temperature of the battery pack or the temperature of the cell is more than a predetermined value is more than a predetermined period of time. The function detecting device may include a device for detecting the temperature at each of at least three points. In this case, the judging device judges whether or not there is a loss of functional status according to whether or not the difference between the temperature at one of the three points and an average value of the temperatures at the other two of the three points is more than a predetermined value. The function detecting device may include a device for measuring the internal impedance at a predetermined temperature. In this case, the judging device judges whether or not there is a loss of functional status according to whether or not the internal impedance is more than a predetermined value. The function detecting device may include a device for detecting a battery voltage, an electric current and a temperature. In this case, when there is a large variation in the battery voltage, the sampling period for detection of the battery voltage, the electric current and the temperature is shortened. The function detecting device and the judging device may have a non-volatile memory for storing detection data and judgment data when there is a drop in battery voltage.
The function detecting device may include a label to be stuck on the battery pack or the cell, the label having a conductor wire or a thin conductive film disposed all over the reverse side thereof. In this case, the judging device judges whether or not there is a loss of functional status according to whether or not the label is separated or whether or not the conductor wire is broken. The function detecting device may include a pressure sensor or an impact sensor. In this case, the judging device judges whether or not there is a loss of functional status according to whether or not a pressure or impact applied to the battery pack is more than a predetermined value, or whether or not a pressure or impact more than a predetermined value has been applied to the battery pack more than a predetermined number of times, or whether or not a pressure or impact more than a predetermined value has been applied to the battery pack for more than a predetermined period of time. The function detecting device may include a strain sensor for detecting a strain on the battery pack. In this case, the judging device judges whether or not there is a loss of functional status according to whether or not the strain is more than a predetermined value. The function detecting device may include a gas sensor for detecting a leakage of the electrolyte. In this case, the judging device judges whether or not there is a loss of functional status according to whether or not the value of detected gas leakage is more than a predetermined value. The function detecting device may include one or a plurality of thermal fuses disposed at places on the circuit board where heat may be generated. In this case, the judging device judges that there is a loss of functional status from fusing of any of the thermal fuses.
In addition, the arrangement may be such that on condition that the judging device has judged that there is a loss of functional status, the control device disables charging or both charging and discharging through the charge-and-discharge control device and moreover forcedly discharges each cell of the battery pack through the forced discharge control device. The charge-and-discharge control device may disable charging or both charging and discharging through a semiconductor device for on-off controlling charging and discharging or a thermal fuse inserted in the current path for charging and discharging, the thermal fuse being fused when charging or both charging and discharging are to be disabled. The arrangement may also be such that according to the judgment concerning a loss of functional status made by the judging device, the control device performs one of the operation of disabling charging or both charging and discharging, the operation of inhibiting charging or both charging and discharging and the operation of stopping charging or discharging by controlling the charge-and-discharge control device and forcedly discharges each cell by controlling the forced discharge control device and further performs control for issuing an alarm according to need. In addition, the control device may perform control for filling a flame-resisting substance into the battery pack according to the judgment concerning a loss of functional status made by the judgment device.
In addition, the present invention provides a battery pack arranged to make a judgment concerning a loss of functional status and to perform selectively charge-and-discharge control and forced discharge control according to the judgment. The battery pack includes a charge-and-discharge control device for charging and discharging a battery and a forced discharge control device for forcedly discharging each cell. A liquid detecting device detects a liquid leakage in the battery pack. A control device disables charging or both charging and discharging by controlling the charge-and-discharge control device and forcedly discharges each cell of the battery pack by controlling the forced discharge control device on condition that a liquid leakage has been detected by the liquid detecting device. The control for disabling charging or both charging and discharging may be performed through a fusible portion that is fused by detecting a liquid.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.